Perceptual constancy is an important aspect of our interaction with the world. The size constancy is the easiest one to understand. For example, two telephone poles look the same size when the first is viewed from 100 meters and when the second is viewed from 1 meter, even though the visual angle is very different. A person who appears to be 6 feet tall when he is nearby also appears to be 6 feet tall when he is standing across the room. Now, think of a penny… and you will understand the shape constancy in which the penny looks round both when viewed head on and when viewed from an acute angle. The color constancy is a little more difficult to grasp… think of the color of your car, for example… if you don’t have one, think of the one you are always taking a ride… you always perceive the color of the car as uniform, even under different light sources (sunlight, artificial light, shade). These are few examples of perceptual constancy that are essential to make our lives more stable, letting us freer to worry about other types of non-constancies (Goldstein, 2011; Cohen, forthcoming).

Here are some photos by Audrey Heller that plays with the phenomenon of size constancy: